System of motor control.



E. L. GALE, Sin. SYSTEM OF MOTOR CONTROL.

APPLIOATION FILED OUT. 9, 1907.

965,175. Patented July 26, 1910.

a SHEETS-SEEM 1.

WITNESSES: INVENTOR BY g ZM Wm n. L. GALE, s3. SYSTEM OF MOTOR CONTROL.APPLICATION FILED 00'1". 9; 1907.

965,175. Patented July 26, 1910.

3 SHEETS-SHEET 2.

E. L; GALE, s3. SYSTEM OF MOTOR CONTROL. APPLICATION FILED OCT. 9, 1907Patented July 26, 1910.

3 SHEETS-SHEET 3.

I l2 (/3 S -001N aim "'trates the adaptation of my invention to anUNITED STATES PATENT OFFICE.

ERNEST L. GALE, SR., 015 YONKERS, NEW YORK, ASSIGNOR T0 OTIS ELEVATORCOMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

SYSTEM 015 MOTOR CONTROL.

I Specification of Letters Patent.

Application filed. October 9, 1907.

Patented July 26, 1910.

' Serial No. 396,533.

To all whom it may concern:

Be it known that I, ERNEST L. GALE, Sr., a citizen of the UnitedStates,residing at Yonkers, in the. county of Westchester and State of NewYork, have invented a new and useful Improvement in Systems of HotorControl, of which the following is a specification.

My invention relates to the control of electric motors, and one of itsobjects is-to provide improved means whereb the starting andaccelerating of an electriomotor under various conditions is etlicientlyand automatically controlled, and to these ends it includessubstantially the various features of construction and arrangement ofparts having the general mode of operation substantially as hereinaftermore particularly pointed out.

The accompanying drawings illustrate diagrammatically variousmodifications of my invention.

Figures 1, 2, 3, 4 and 5 show various ways of applying my invention toeffect the control of an electric motor; and Fig. 6 illuselectricelevator system.

Like reference characters designate similar parts throughout the variousviews.

Figs. 1, 2 and 3 are very similar, the essential difl'erence being inthe relative positions of the motor, starting resistances and the seriesfield winding.

Referring more particularly. to Figs. 1, 2 and 3, 1 designates a mainline two-pole switch which serves to connect the positive and negativesup ly mains and respectively, and ieading' from a suitable source ofcurrent supply, to the motor controlling system by means of the wires orconductors 2 and 3. M designates an electric motor armature providedwith brushes 20 and 21, while 4 and 5 designate respectively the seriesand shunt field windings. 13 designates a resistance of relatively hightemperature co-eificient, that.is, a self-increasing resistance, in thatasthe current through the same continues to flow the resistance willbecome heated and increase in ohmic value. 12 and 11 designateresistances of relatively low temperature co-eflicient, or suchresistances as are not appreciably selfincreasing or self-reducing. 33designates an accelerating magnet for controlling the switches 91, 92,93and 94. 15 designates an electro-magnet for controlling the switch 16,and 14 designates an auxiliary resistance normally in series with thewinding of the accelerating magnet.

Assuming that the main line switch 1 is closed in Fig. 1 and that themains and are connected to a suitable source of current supply of theproper potential, current will flow by wire 2 and brush 21 through themotor armature M to brush 20, and thence by wire 19 through theself-increasing resistance 13, the ordinary resistances 12 and 11,conductor 6, series field winding 4, and conductors 8 and 3 to thenegative main. The shunt field winding 5 is connected directly acrossthe mains by the conductor 2 on one side and the conductors 10 and 3 onthe other. The accelerating magnet 33 is connected by the conductor 34to the armature brush 21, and by the conductor 18 and resistance 14 tothe brush 20. The accelerating magnet is therefore in series with theresistance 14 in a circuit connected directly across themotor armature.Since the motor armature and field circuits are closed, the motor willstart, the resistances 13, 12 and 11 allowing sufiicient current to passprovided the motor is not overloaded. Since the accelerating magnet 33is connected across the motor armature,-it does not receive sufficientcurrent to close the switches '91, 92, 93 and 94 until after the motorhas started, because before the switch 91 is closed the drop ofpotential across the motor armature is at a minimum, substantially allof the drop being across the starting resist anc es 13, 12 and 11 andseries field 4. When the motor armature begins to rotate, however, thedrop across the latter gradually increases, so that the acceleratinmagnet becomes gradually strengthene until the latter has sufficientstrength to close the switch 91 by lifting the armature 25 against thepole 29, the said armature pole being also a contact of the switch 91.The closure of the switch 91 short-circuits the self-increasingresistance 13 through the low resistance conductor 22. This enables themotor to receive more current and increase in speed until the potential,across the brushes is such that the accelerating magnet 33 closes theswitch 92 by attracting the contact' 26 against the pole 30 andshort-circuiting the resistance section 12. This produces a. furtherincrease in the motor speed until the switch 93 is operated to closedposition by the connection of the contacts 27 and 31, therebyshort-circuiting the section 11 of the startlng resistance and also aportion of the series field winding 4:- 'As the motor increases stillfurther in speed and the accelerating magnet becomes still stronger, theswitch 94 is finally operated by the connection of the contacts 28 and32, thus short-circuiting the remaining section of the series fieldwinding, after which the motor accelerates to full normal speed andoperates as a simple shunt motor.

The above operation is repeated every time the motor is started providedthe load upon the motor is normal. If the load should be a little abovenormal the starting resistance would not let sufficient current pass toenable the motor to receive sufiicient power to move the load.Consequently the accelerating magnet would not operate to short-circuitthe starting resistance,'and the latter after a time would thereforebecome over-heated. One of the objects of my invention is to provideautomatic means for starting the motor, even though the same beoverloaded. This I accomplish by means of a switch 16 and anelectro-magnet 15 and connections between the same and the hightemperature co-eflic ient resistance or self-increasing resistance 13.This resistance 13 is preferably made of iron wire, galvanized if esiredto prevent rusting, or it may be" made of any other material having arelatively high temperature co-efiicient, so that as current flowsthrough the same the resistance thereof will be increased automaticallyat apredetermined rate. In this instance the magnet 15 is connected tothe terminals of the resistance 13, and therefore is made to depend forits operation upon an increased difference of potential across theresistance 13, the electro-magnet being so adjusted that normally itdoes not become sufficiently energized to close the normally open switch16 operatively connected thereto. If the main switch 1 is closed and themotor refuses to start,'or if it starts and operates at very slow speedso that current will flowthrough-the. starting resistance for) too longa time, the potential across the resistance 13 is at first notsufficient to effect the energization of the magnet 15. 'As the currentcontinues to flow, however,-the reslstance 13 becomes heated, and owingto its relatively high temperature co-eflicient its resistanceincreases, thus increasing the drop of potential across the resistance13 and therefore'also across the terminals of the magnet 15. In otherwords, the resistance 13 and magnet 15 are connected in parallel and acertain amount of current W111 flow' through each path, and whenthe'resistance mno f the path including the resistance 13v increasesmore current will flow through the path containing the magnet 15 until apredetermined length of time elapses when the latter will besufliciently energized to close the switch 16, therebyelectrically'connecting one terminal of the accelerating magnet 33 tosome point in the armature circuit or in the starting resistance, as thepoint 17 on the resistance 13, by way of the conductors l8 and 89.

The closure of the switch 16 in Fig. 1

takes the resistance 14 from in series with the winding of theelectro-magnet 33 and places it in parallel with a portion of theresistance 13 in the armature circuit. The

starting resistance is therefore somewhat reduced, but the principaleffect produced is that the potential applied to the accelerating magnet33 is increased, since it is now connected between the brush 21- and thepoint 17 or across the motorarmature and a portion of the startingresistance in series with each other. There being an overload thearmature resistance will be very low, but when the resistance isconnected in the manner explained by the switch,16 more current will beshunted through the accelerating magnet to make the latter morepowerful. This will be evident when it is noted that from the point thecurrent flows through two paths, one through the conductor 34,accelerating magnet 33,.conductor 18, switch 16 and conductor 89 to thepoint 17 and the other from the point 90 through the armature M,conductor 19 toithe junction 95,'and thence through the". resistance 14:and a portion of the resistance 13 in parallel with each other to thepoint 17. If the current passing through the accelerating magnet 33, dueto the increased potential across its terminals, is now suflicient theswitch 91 will be operated to closed position to short-circuit theresistance 13 and also the magnet 15, thus allowing the resistance tocool and preventing magnet 15 from consuming current. The resistance 14will therefore again be placed in series with the accelerating magnetwinding, but it should be understood that it requires much less powerfor the accelerating magnet to hold the switch 91'closed than to firstoperate it to closed position. The accelerating magnet will thereforestill have sufficient strength to hold the switch 91 in closed position.The resistance 13 having been cut out, the current through the motor maybe sufficient to cause the motor to accelerate and one or more of theremaining accelerating switches to be closed. The motor, however, underthe present conditions of overload, does not accelerate to full speedsince the'potential across themotor does not reacha valuesufficiently-high to enable the accelerating magnet 33 to close the lastswitches. due to the relatively-low counter-electromotive force of themotor'armature rotating This is o I at lower speed under overloadedconditions.

At least the last switch 94 must therefore remain open and a portion ofthe series field remain in circuit. In this connection it will be notedthat while the switch 94 is open, the accelerating magnet- 33 does notreceive the full line potential, owing to the drop in po tential throughthe portion of the field winding'4 which is at this time in series withthe armature. This difference in potential may be sufficient to controlthe operation of the switch 94; in other words, the drop in potentialacross the mains on the one hand might be ample to effect the closing ofthe switch 94 while on the other hand the fall of potential through theaccelerating magnet would be insuflicient to operate said switch. It isto be further noted that there is found in practice to be a materialdifference between the line otential with a light load and with a heavyoad. This drop in potential across the mains as the load increases is initself suiiicient to control the switch 94 so that it an elevatorsystem, is designed to lift its normal load at normal full speed, and inorder to insure a constant speed it is necessary to have a substantiallyconstant field strength and this necessitates a shunt wound motor. Whileit is customary to'provide such a motor with a series field, in orderthat the field strength may be gradually in creased while starting aload so as to keep the starting current at a minimum, the series fieldis usually cut out of circuit after the v motor has started and the samethereafter runs at its normal full speed with the shunt field windingalone excited. Furthermore, the usual type of motor controllingapparatus starts and accelerates the motor to full speed by firstcutting out the starting resistance and then the series field, if suchis used. Such controlling means operates substantially in the samemanner, regardless of the load upon the motor, and the period of time inwhich the current is first supplied to the motor. It is readily seenthat when a motor is overloaded or loaded beyond a predetermined limitand the motor is started and accelerated to full speed in the usualmanner the motor is required to operate such overload at its full speed,which might injure the motor armature. My invention provides especiallyfor this overload feature, in that it automatically operates to bringthe motor to full speed by gradually short-circuiting the startingresistance and then cutting out the series field if the load on themotor is normal or below a predetermined limit, but where the load issomewhat above normal the series field or a portion thereof will remainin circuit with the motor armature and the motor is therefore enabled tolift or actuate this overload at slow speed and maximum torque withlittle danger of injury to the motor armature.

By adjusting the positions of the movable contacts of the acceleratingswitches either the last switch 94 alone may be left open or both theswitches 93 and 94. In this way it is possible to keep in circuit eitherthe en I tire series field winding'or only a portion thereof, or, as inFig. 1, the entire series field winding 4 and a portion 11 of thestarting resistance may be left in circuit with the motor armature. Suchadjustments may be carried to any refinement desired, depending upon thenumber of steps in which the starting resistance and series fieldwinding are cut out. If, however, the overload on the motor uponstarting is excessive and the current fiowing through the motor sistancein the latter being comparatively low. 4

It is readily seen from the foregoing that not only is the starting andaccelerating of the motor under ordinary loads entirely automatic, butalso when the motor is overloaded to some extent, sufficient starting resistance is automatically cut out of circuit to allow themotor to start,unless, of course, the overload is excessive, in which case theremaining starting resistance is kept in circuit, thereby protecting themotor from damage caused by an abnormal How of current.

In the modification illustrated in Fig. 2 one terminal of theaccelerating magnet 33 is connected to the brush 21 as in Fig. 1, whilethe other terminal is connected through the auxiliary resistance 14 toone extremity of the section 11 of the starting resistance at the point35. While in Fig. 1 the accelerating magnet 33 is connected in serieswith the auxiliary resistance 14 in a circuit connected across the motorarmature, in Fi 2 the accelerating magnet 33 is eonnectef in ,motorarmature and the series field winding 4 in series with each other.Furthermore, in Fig. 2 the entire series field, except on overload, iscut out of circuit by the last switch 94 to be operatedto closedposition after all the starting resistances have beencut out of circuit.In Fig. Q'the accelerating switches operate from right to left, whereasin Fig. 1 they operate from left to Tight.

The operation of Fig. 2 on overload is as follows. Assuming the switch 1to be closed and connected to a suitable source of current supply,current will flow through the armature M, series field winding 4 andsections 11, 12 and 13 of the starting resistance to the negative lead3. Current will also flow through the shunt field circuit 5 by way ofthe conductor 10. The accelerating magnet 33 receives current throughthe conductor 34 from the point 90 and through the conductor 18 andresistance 14-to the point 35.

The load being above normal the resistance of the circuit including thearmature and the series field 4 will be very low and the acceleratingmagnet cannot close any of its switches. As the current continues toflow the self-increasing resistance 13 causes more current, to beshunted through the electromagnet 15 until finally or after apredetermined time passes the latter closes the switch 16, whereupon theresistance 14 will be removed from the circuit including theaccelerating ma et 33 and placed in parallel with a portion of thestarting resistance 11. i The potential applied to the acceleratingmagnet 33 will therefore now be established between the point 90 and thepoint 17 and including in circuit the motor armature, the series fieldwindlng 4 and the resistance 14and a portion of the resistance 11 inparallel with each other. Provided the load is not excessive this willcause the electro-magnet 33 to receive'sufi'icient current to close theswitch 91. The closure of the latter switch will short-circuit theresistance 13 and the electro-magnet 15, whereupon the switch 16 willagain be opened and the resistance 14 again be placed in the circuitwith the magnet 33. But as, before explained, less power is required tohold the switch 91 closed than to first close it. The motor maytherefore start upon receiving more current, due to the short-circuitingof the resistance 13, and as the motor accelerates the acceleratingmagnet 33 will in- .cause the motor to operate with strong torque but atslow speed.

In Fig. 3 the accelerating magnet 33 and auxiliary resistance 14 are inseries with each other in a circuit connected between the points 90 and95 or across a portion of the armature circuit including the armature Mand a. small portion of the starting resistance 11; The series fieldwinding 4 is arranged to be cut out in one step by the switch 94 whichoperates last. The general operation of Fig. 3 is about the same as in'Figs. 1 and 2. In each case the motor is started and accelerated tofull speed except in cases of overload, by first short-circuiting theself-increasing resistance or high tempenature co-eflicient resistance13, after which the remaining sections of. the starting resistances areshort-circuited step by step and finally the series field winding isshort-circuited and the motor runs at full speed as a simple shuntmotor, except, in cases of overload.

In each of Figs.- 1, 2 and 3 it will be noticed that one terminal of theaccelerating magnet is connected to the brush 21 and in each' figure theelectro-magnet 33 is connected in series with the auxiliary resistancevarious ways in which the acceleratingmagnet may be strengthened whentheself-increasing resistance-is cut out. The overload feature in eachcase is also substantially the 14, but the latter is connecteddifierently in each figure to the'starting reslstance to show.

same, in that where itis desired to start the -motor with an overloadthe starting current lra'pidly heats the high temperature cofli: "cientresistance or self-increasing resistance 13, thereby increasing itsohmic resistance and drop of potential across the terminals thereof andtherefore enabling the magnet 15 to increase in strength sufiiciently toclose.

the switch 16. As before pointed out, the closure of the latter willenable the acceleratlng magnet to close one of its switches 'and allowmore starting current to flow through the motor, that is, sufficientcurrent to start the motor unless the overload is excessive.

In Fig. 4 is illustrated a modification in which, instead of theself-increasing or high temperature co-eflicient resistance 13, aresistance 13, havinga negative temperature co-efficient, is used; thatis, the resistance 13 is formed of a material whose electricalresistance decreases as the temperature rises.

It is well known that certain substances,

such as carbon and raphite, or magnetite,

have the property 0 lowering their resistance to the passage of electriccurrent when they are heated by the latter or otherwise.

And it is also well known that where one or more resistance elementsform part of an electric circuit and the resistance of one element' ischanged, the drop in potential or the'voltage across the terminals ofsuch .resistance element will vary.

In Fig. 4, 13 designates such a self-reducin'g resistance, comprising inthis inv the middle switch 91is an auxiliary switch 96, comprising aspring-pressed contact 43 and a movable contact 42. 15 designates anelectro-magnet for operating the switch 16 and is connected across aportion of the self-reducing resistance 13 between the points 23 and 97.36 designates an additional magnet for operating the-switch 98.

.The operation of the system shown in Fig. 4 is as follows. Upon closingthe main line switch 1 a circuit is closed through the motor armature,self-reducing resistance 13, resistance 12, series field winding 4, to vthe negative main by conductor 8. A circuit is also closed through theshunt field winding 5 which is connected directly across the mains. Ifthe motor is required to operate only a normal load the motor will startat once, the current being limited by the starting resistances 13, 12,and the series field winding 4. The accelerating magnet 33 does notreceive current immediately, since its circuit is open at the switch 96and also at the switches 39-and 41. The magnet 15, however, is soadjusted that it at once receives sutlicient current to operate theswitch 16 by bringing into electrical engagement the contacts 37 andseparating the contacts 38. The resistance 13' being a self-reducingresistance, the resistance of the latter is at first comparatively lowand consequently maximum current will at first be shunted through themagnet 15'.

Upon theconnection of the contacts 37 the magnet 36 will be connected bythe conductors 46, 45 and 47 across a portion 99 of the section 12 ofthe starting resistance be tween the points 100 and 101. This portion 99of the resistance 12 will be sufficient to cause the electro-magnet' 36to close the switch 98 or connect the contacts 39, 40 and 41. A circuitfor the accelerating magnet will then be closed from the point 90through the conductor 34, winding of the electro-magnet 33, auxiliaryresistance 14, conductor 44, contacts 41, conductors 48, 49 and 50 tothe point 97 on the self-reducing resistance 13. It should be noted thatthe contacts 38 are still separated and that the switch 96 is open sothat no other path is afforded for current passing through theelectro-magnet 33. The accelerating magnet 33 is now in series with theresistance 14in a circuit connected between the points 90 and 97 oracross a portion of the armature circuit including the armature and asmall portion of the self-reducing resistance 13. As the speed of themotor increases the counter-electro motive force in the armature willcause the accelerating magnet to become stronger and operate the switch91 by connecting the armature 25 to the contact 29. Substantially at the,same time the switch 96 will be closed by connecting the contacts 42,43. The closure of the switch 91 shortcircuits the section 12 of thestarting resistance to permit the motor to run to a higher speed. Theshort-circuiting of the resistance 12, however, will also short-circuitthe magnet 36, whereupon the switch 98 will drop to open position. Thecontacts 41 are therefore separated and the accelerating magnet wouldbecome deenergized were it not for the switch 96 which is closed beforethe magnet 36 is thus deenergized. Preferably the switch 96 is closedbefore the switch 91, otherwise the circuit for the accelerating magnetmight be interrupted at the contacts 41. As the motor increases in speedthe accelerating magnet is still further strengthened by the risingpotential across the motor armature until the switch 92 is closed by theconnection of the contacts 26.and 30. This causes the resistance 13 tobe short-circuited and also the magnet 15. All of the startingresistance is now out out and the magnet 15 is deenergized. The switch16 therefore drops back to its normal position as shown in Fig. 4, thatis, the contacts 37 are again separated and the contacts 38 connected.The accelerating magnet increases in strength as the motor increases inspeed, until finally the switch 93 is closed by the connection of'thearmature 28 with the contact 32, thereby short-clrcuiting the seriesfield winding 4, after which the motor runs at full normal speed as asimple shunt motor. The above described operation as to Fig. 4 takesplace each time the motor is started and accelerated, provided the loadon the latter is normal or below normal'or below a predetermined value.

Again referring to Fig. 4, it should be noted that in case an overload1s thrown upon the motor before starting the operation of the system issomewhat different. If it be assumed that such an overload exists and itisdesired to start the motor, the normal starting current limited inamount by the resistances 13 and 12 would be insufiicient to permit themotor to receive sufficient power to start the load in the mannerheretofore explained. Upon the closure of the switch 1 current will flowand the potentlal across the resistance 13 will be sufficient to enablethe magnet 15 to operate the switch 16 to connect the contacts 37 andseparate the contacts 38. Due to the connection of they contacts 37 themagnet 36 will receive current and operate the multiple switch 98 toclosed position as before. The accelerating magnet 33 and resistance 14are connected in series with each other in a circuit parallel to themotor armature and a small portion of the resistance 13 connected inseries with each other between the points 90 and 97. As the motor isunable to start it does not generate an oounter-electro motive force,and there ore the accelerating magnet will not be sufficiently energizedto operate any of its switches to cut out the starting resistance. Asthe self-reducing resistance 13' becomes heated by the flow of thestarting current through it the potential across the terminals thereof,and also across the terminals of the magnet 15, becomes lowered, sincethis resistance comprises substance which lowers in resistance uponbecoming heated. It is therefore evident that the potential across theterminals of the magnet 15 becomes less and less until finally themagnet is so weakened, or until the proportion of the current passingtherethrough becomes so small that the switch 16 is dropped to itsnormal position, thus separating the contacts 37 and connecting thecontacts 38. A circuit is now closed through the accelerating magnetfrom the point 90 through conductor 34:, winding of the magnet 33,conductor 22, contacts 38, conductor 102, contacts 39,conductor- 52 tothe point 103 on the resistance 13. The separation of the contacts 37does not effect the deenergization of the magnet 36, since. the contacts40 aflord the maintenance of a retaining circuit, the section 12 of thestarting resistance not being short-circuited at th1s time.

The accelerating magnet circuit just traced no longer includes theauxiliary resistance 14 and is now connected between the points 90 and103, or across a portion of the armature circuit including the armatureand the larger portion ofitheresistance 13. The drop of potentialbetween the points 90 and 103 through the armature istherefore greaterand more current will be received by the accelerating magnet to causethe same to close the switches 96 and 91 substantially at the same timeor successively in the order mentioned. The resistance 12 isshort-circuited by the closure of the switch 91 and the'm'agnet 36 isdenergized to permit the multiple switch 98 to be opened. The separationof the contacts 39 will interrupt the connection of the acceleratingmagnet to the point 103, but before the contacts 39 separate theswitch96 is closed to a ain connect the accelerating magnet througthejresistance 14 and conductors 51, 49 and 50 to the point 97. As soonas the resistance 12 is short-circuited the starting current isincreased so .thatthe overload may be operated, As the .motor increasesin speed the accelerating magnet will increase in strength to close thes "tch 92 which will short-circuit the resistance 13'. The last switch93 will remain open, however, since the motor is unable .under theoverload conditions, to cause the accelerating magnet to receivesuflicient current to actuate the last armature 28. The series fieldwinding 4 therefore remains in circuit and the motor continues to rotateat slow speed but with strong torque or as a compound motor.

The system shown in Fig. 5 is very much like that shown in Figs. 1, 2and 3. In this instance a coil 15" is wound directly on one pole orpolar branch of the acceleratinginagnet core and it is so 'wound as toassist the winding of the acceleratin magnet. As in the other figures,the acce eratmg magnet, where the load on the motor upon starting isnormal, -first operates the switches to cut out the starting resistancestep by step and finally the series field, permitting the motor to runat full normal speed. But

where the motor is overloaded and the sameis unable to start, the heatgenerated in the high temperature co-efiicient resistance orself-increasing resistance 13 causes the latter to increase itsresistance and the otential across it causes the coil 15, to receivemore current and therefore close the switch 91. The closure of theswitch 91 short-circuits the resistance 13 and also the coil 15", butthe accelerating magnet between the points 90 and 97 will havesufficient strength to hold the switch 91 closed. The motor willtherefore receive additional starting current and if the motor startsthe accelerating. magnet will automatically cut out the remainingstarting resistance sections 11 and 12 by the operation'of the switches92 and 93. If the motor is so heavily overloaded, however, that itcannot start, no more resistance will be cut out and the latter willsimply become heated by thecurrent. The arran ement is preferably suchthat when the load is beyond normal butless than a redetermined maximum,the current wil be increased sufiiciently by the automatic cutting outof the resistance 13 that it will start and accelerate, one or more ofthe last switches, however, remaining open, as that designated 94, sothat the series field winding 4 will still remain in circuit. For anoverload therefore the motor will be automatically started andaccelerated, but its 0 eratin speed will be lower than normal, ue to t eretaining of the series field winding 4; in circuit, but as explainedbefore when the series field windlng remains 'in circuit the torque ofthe motor is greater, the motor operating as a comother of which passesover the sheaves 83 and is wound about. the hoisting drum 64. This drumis connected by intermediate mechanism-teen electric motor M. 63designates electro-magnetic brake apparatus.

- 53 and 54 designate reversing switches which in construction andcomprise movable plates or bridging members connected to be actuated byelectro-magnets including the solenoids 81 and 82. The two contactplates 78 and 79 are connected to but insulated from a rod, to the upperend of which is connected a core or plunger extending into the solenoid81. In this instance the plates are shown electrically isolated normallyby being supported on fixed stops. When the solenoid 81 receives currentthe plates 78 and 7 9. are lifted, the former to electrically connectthe contacts 73 and 75, and the latter to electrically connect thecontacts 77 and 76.

When the switch S in the car C is operated by moving the lever onto thecontact 65 a circuit is closed through the main line' switch 1 from thepositive main through conductors 2, 72 and 70, through the solenoid 81,and thence through the conductor 69 to the negative main. By moving thelever 67 in the opposite direction onto the contact 66 a circuit isclosed through the conductor 71 instead of the conductor 70, and thencethrough the solenoid 82 -to the negative main. It .should be understoodthat the reversing switch mechanism, as well as the motor, brakeapparatus, and hoisting device and connections, are shown here merely byway 'of'illust-ration and that these parts may be substituted by othersperforming similar functions if desired.

The accelerating apparatus comprises a series of electro-magnets and aseries of corresponding switches operated thereby to control thestarting resistance including as a section thereof the self-increasingresistance 13. It will be noticed that instead of,

a single magnet having a plurality of polar projections or operatingswitches, I have in this mstance shown a series of electric relays.These relays are so adjusted that the switch 59 will be the first toclose to short- A circuit .is then closed from the positive conductor 2by way of contacts 73, 78 and 75, conductor 86 to the armature brush 21,

and thence through the armature'to brush '20, conductor 19, contacts 76,79 and '77, wires 80 and 85 to one terminal of the resistance 11. Thecircuit continues through the resistances 11, 12and 13, conductor 6,

series field winding 1 to the conductor 3, and thence to the negativemain. A circuit is also closed from the positive main through contacts73, 78 and 74, conductor 104, the electro-magnet of the brake apparatus63 and conductorv 3 to the negative main: A circuit is also closed fromthe positive main through conductor 104 and shunt field winding 5 to thenegative main. It should also be noted that the terminal 90 is connectedthrough a portion of the conductor 101 and contacts 7 1, 75 andconductor 86 to the armature brush 21. The other terminal of the circuitincluding the electro-magnets 58, 57, 56 and 55 is connected to thepoint 97 on the section 11 of the starting resistance, and

thence through the conductor 85, contacts 77, 79, 76, and conductor 19to the brush 20 of the motor armature. The series of acceleratingmagnets are therefore connected in series with a portion of the section11 in a circuit connected directly across. the motor armature. Theaccelerating magnets therefore depend for their operation upon thecounter-electro motive force developed J11 the motor armature.

' When the switch 53 is closed by moving the switch lever 67 onto thecontact 65 the brake apparatus will be'released and the motor willreceive current limited by the starting resistance sections 11, 12 and13, and the same is therefore free to start to operate the hoisting drum64 to lift or lower the car C. As the motor increases in speed themagnet 55 will be the first to operateto close the switch 59, thusshort-circuiting the resistance 13. The 'electro-magnets 56, 57

. and 58 will then operate successively to close the switches 60, 61 and62, respectively, to cut out step by step the resistances 12 and 11 andthe series field winding 4. The motor will then attain its full normalspeed.

In order to stop the-elevator car the lever 67 is brought back to itscentral position, thereby opening the circuit of the solenoid 81 whichin turn efitects the opening of the switch 53, the cutting 015? of thecurrent from the electro-magnet brake and from the motor. The brake willtherefore be applied, that is, spring-pressed brake shoes or other wellknown means will be brought against .the brake pulley on the motorshaft. \Vhen the load on the motor exceeds a predetermined normal but isless than a predetermined maximum, and the motor therefore refuses tostart upon the closing of one of the reversing switches, the startingcurrent flowing through the starting resistance for a short length oftime will heat up such resistance. The section 13 being aself-1ncreasing resistance or a high temperature c oefficient resistancewill heat more rapidly than the sections 11 and 12. The potential acrossthe terminals of the resistance 13 will therefore increase to such anextent that the winding 15 connected to such terminals will receiveafter a predetermined time suffi-' 55 that when both solenoids receivecurrent they assist each other in tending to close the switch 59. Whenthe armature does not start or when the counter-electromotive forcedeveloped in the armature is not sufficient the magnet 55 will notreceive suflicient current to close the switch 59, but when theresistance 13 is heated and more current passes through the solenoid 15the switch 59 will be closed to short-circuit the resistance.

sistance 13. This will permit more current to be received by the motorarmature, there fore making the motor more powerful at the start to movethe overload. After the .motor starts it will accelerate in speed andbuild up counter-electromotive force which shunts more current throughthe accelerating magnets to cause the latter 'to operate their switchessuccessively to cut out the remaining sections 12 and 11 of thestarting. re-

The load being beyond normal, however, the last switch 62 will remainopen so as to retain in circuit the series field winding l, which asbefore explained causes the motor to operate as a compound motor havingstronger torque than a shunt motor but lower speed. In some cases theswitch 61 may also remain open. The number of steps desired in cuttingout the stanting resistance will depend upon the refinement of operationdesired' The successive operation of the accelerating magnets may beobtained in several specifically different ways. For instance, they mayhave different numbers of ampere turns, or the cores of the magnets'maybe placed in different relative positions in their respective solenoids.

In all of the figures of the accompanying drawings I have shown myinvention applied to an electric motor-controlling system,

and particularly to motor-controlling apparatus for an elevator system.It..may,' however, be readily applied to the electrical control oftranslating dev ices other than an electric motor.

Obviously those skilled in the art may make various changes in thedetails and arrangement of parts without departing from thespirit andscope of my invention and I desire therefore not to be limited to theprecise construction and connections'herein disclosed. g d What I claimand desire to have protected by Letterslatent of the United States is'1. In motorcontrolling apparatus, the combination with an electncmotor, of starting resistance therefor, means for controlling saidresistance toeifect an acceleration of the motor with normal load, andmeans permitting the operation of said controlling-means for overload.

2. In motorcontrolling apparatus, the combination with an electricmotor, of accelerating apparatus therefor, and means for modifying thelatter automatically to permit the operation of the same when the loadon the motor exceeds a predetermined value.

3. In motor-controlling apparatus, the

combination with an electric motor, of ac-' latter even when the load onthe motor exceeds a normal starting or running value.

5. In motor-controlling apparatus, the combination with an electricmotor, of sectional starting resistance therefor, electromagneticmechanism for varying said resistance to effect an acceleration of themotor, means for automatically strengthening said electro-magneticmechanism when the load on the motor exceeds a predetermined value, andconnections to reestablish the normal circuitof the electromagneticmechanism after the motor attains a predetermined speed.

6. The combination with an electric motor, of starting resistance, aseries of switches for varying said resistance, electro-magnetic meansfor operating said switches successively to cut out the said resistancestep .by step and effect an acceleration of the motor, anelectro-responsive device operated upon variation of the drop ofpotential along a portion of said resistance to a predetermined value tochange the circuit of the said electro-magnetic means to strengthen thesame when the latter does not operate said. switches after apredetermined length of time, and connections efiecting the cutting outof said electro-responsive device and the restoration of the circuit ofsaid electromagnetic means when the first switch is operated.

7 The combination witli an electric motor,

of starting resistance therefor, art being of low temperaturecoefficient an part being of comparatively high temperature coefiicient,means for automatically cutting out said resistance gradually as themotor increases in speed, and means dependent upon increase of potentialdrop in said h h temthe motor does not start or does not increase inspeed sufficiently to cause the operation of said cutting-out-means.

8. The combination with an electric motor,

of starting resistance therefor compnsing a.

out-means when the load on the motor ex-' ceeds a predetermined value.

9. In motor-controlling apparatus, the combination with a compound-woundmotor, of a resistance of low temperature coeflicient and aresistance'of high temperature coeflicient both in series with the motorarmature and the series field winding, electric switches for cutting outsaid resistances, electro-magnetic means for operating said switches,and an electro-responsive device 0 erated automatically to stren hensaid e ectro-magnetic means when the oad on the motor exceeds apredetermined value.

10. In motor-controlling apparatus, the combination with a motorarmature and a series field winding, of a resistance of high temperaturecoefficient in circuit with said motor armature and series fieldwinding, multiple electro-ma netic switch mechanism for cutting out sairesistances in steps to efiect a gradual acceleration of the motor, andmeans dependent upon variation of drop of potential across saidresistance to efiect a strengthening of said electro-magnetic mechanism.

11. In motor-controlling apparatus, the combination with a motorarmature, a shunt field winding and a series field winding, of aresistance of high temperature coefiicient and a resistance of lowtemperature costlicient in series with the motor armature and seriesfield winding, electro-magnetic switch mechanism for cutting out saidresistances and said series field winding in steps to effect a gradualacceleration of the motor, and means dependent upon variation ofpotential along one of said resistances to strengthen saidelectrosmagnetic mechanism when the load on the motor exceeds apredetermined value.

/resistance ofhigh temperature coeflicient and a resistance of lowtemperature coefli cient in series with the motor armature, automaticapparatus for cutting out said resistances step by ste and means deendent u on variation 0 drop in potentlal in one 0 said resistances tostrengthen said apparatus when the load on the motor exceeds apredeterminedvalue or its speed of rotation does not reach apredetermined value after the lapse of a predetermined time.

13. The combinatlon with an electric motor, of a sectional startingresistance therefor comprising a section of comparatively hightemperature coefiicient and a section of low temperature coefiicient,means for successively and automatically cutting out said sections asthe motor increases in speed, beginnin with a section of hightemperature -coeflic1ent, and means dependent, upon increase ofpotential drop in said section of high temperature coefficient to cffeetthe operation of said cutting-out means by increasing the currenttherein when the load on the motor is so great as to prevent suificientcounter-electromotive force to be produced to effect the operation ofsaid outting-out-means. I

14:. In motor-controlling apparatus, the combination with an electricmotor, of sectional starting resistance therefor comprising a section ofhigh temperature coeificient and a section of low temperaturecoefiicient wherein the drop of potential increases as such section isheated by current flow, electro-magnetic means for successively cuttingout said sections of the starting resistance, an electro-magnetconnected across said section of high temperature coefficient, and aswitch controlled by said electro-ma-gnet for ,varying the electricalconnection of said heating by electric current flow, an electro magnetconnected across the motor armature, a series of switches controlled bysaid electro-magnet for successively cutting out said sectional startingresistance, beginning with said section of high temperature coeflicientas the motor increases in speed, an electro-magnet'connected to saidsection of high tern erature coefficient so as to be dependent or itsenergization upon the variation of the drop in otential in said section,

' and a switch cont-r0 led by said last-named electro-magnet to vary theconnection of said acceleratin magnet to effect an increase of potentialapplied to the latter to increase its power when the load on the motoris so great as to prevent it from starting or from increasingsufliciently in speed to build up sufiicent counter-electromotive forceto eifect the normal operation of said accelerating electro-ma et.

16. In motor-control ing apparatus, the

and a switch operated by said electr0-mag-.

net after current flows through said section a predetermined length oftime to connect one terminal of the accelerating magnet at anintermediate point in the sectional starting resistance to efiect anincrease of potential applied to said accelerating magnet.

17. In motor-controlling apparatus, the

' combination with an electric motor, of an accelerating magnet, aresistance connected in series with said magnet in a circuit connecteddirectly across the motor armature, sectional starting resistance inseries with the motor armature and comprising a section of lowtemperature coefficient and a section of comparatively high temperaturecoefficient, the drop of potential increasing rapidly in the latter due'to heating by the current, a plurality of switches operated bysaidelectro-magnet to successively cut out the sections of. the startingresistance beginning with a section of high temperature coefficient, anadditional magnet connected to separated points along said section ofhigh temperature coefficient, and a switch operated by said additionalelectro-magnet to short-circuit said first-named resistance and aportion of the sectional starting resistance to increase the power ofthe accelerating magnet when the motor armature does not increase inspeed due to a load thereon exceeding a normal maximum.

18. In motor-controlling apparatus, the combination with acompound-wound motor, of sectional starting resistance in circuit withthe motor armature and series field winding, 21 part of said resistancebeing composed of material to rapidly change the drop of potential alongthe latter due to heating therein, an accelerating magnet connected in acircuit across the. motor armature, an electro-responsive devicedependent upon the aforesaid variation of potential to change theconnection of said accelerating magnet to increase the potential appliedthereto when the motor does not start after a predetermined length oftime, switches operated by said accelerating magnet to gradually cut outsaid resistance and series field when'the load on the motor is below apredetermined value and to leave in circuit said series field winding ora por-- tion thereof when the load exceeds a predetermined value, andconnections to effect the cutting out of the electro-responsive deviceand the said part of the starting resistance appreciably affected byheat to restore the circuitof the accelerating magnet when the firstswitch is operated by the latter.

19. In motor-controlling apparatus, the combination with an electricmotor, of starting resistance therefor, a part of which is of hightemperature coefiicient, accelerating electro-m-agnetic mechanism, aplurality of switches operated by said electro-magnet mechanism to cutout said starting resistance step by step, and an electro-magnetwindingco-acting with a portion of the electro-magnetic mechanism toincrease the action of the latter after current has flowed through saidpart of high temperature coefficient a predetermined length of time.

20. In an elevator, the combination with a car, hoisting apparatus, andan electric motor, of reversing switches for the motor, a plurality ofsections of starting resistance, one of said sections changing itsresistance rapidlyand automatically due to heating by current flow, aplurality of electro-magnetic switches for cutting out successively saidsections of starting resistance, beginning with the section along whichthe drop in potential varies rapidly after current begins to passtherethrough, and an auxiliary electro-magnet connected across said.section appreciably affected by heat to assist the electro-magnet of theswitch controlling said last-named section.

In testimony whereof, I have signed my name to this specification inthepresence of two subscribing witnesses.

ERNEST L. GALE, SR.

Witnesses:

CHAS. M. NISSEN, JAMES G. BETHELL.

